MathDB
2021 Combo #9: Region path counting

Source:

May 30, 2021
Combo

Problem Statement

An up-right path between two lattice points PP and QQ is a path from PP to QQ that takes steps of length 11 unit either up or to the right.
How many up-right paths from (0,0)(0, 0) to (7,7),(7, 7), when drawn in the plane with the line y=xāˆ’2.021y = x - 2.021, enclose exactly one bounded region below that line?
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